I think in that case it would be 日本語の勉強が好きだ as 勉強 without する is a noun and not a verb.

furrykef wrote:
I dunno if the nuance is exactly the same or not, but in this case it seems to be unnecessary to use する to turn the noun into an verb, then の to turn it back into a noun. Or am I mistaken?

Though as nuance goes, I think the difference is something along the lines of I like to study Japanese instead of I like the study of Japanese

I dunno if the nuance is exactly the same or not, but in this case it seems to be unnecessary to use する to turn the noun into an verb, then の to turn it back into a noun. Or am I mistaken?

The problem is that を has to connect a noun to a predicate (and in general, the predicate has to be a verb that the subject has control over). 勉強 by itself is not a predicate, it's just a noun. It only becomes a predicate when you attach the copula or する to it.

日本語の勉強 is fine because [noun + の + noun] is a valid grammatical construction.
日本語を勉強する is fine because [noun + を + predicate] is a valid grammatical construction.
日本語を勉強 is not OK because [noun + を + noun] is not valid.

(Actually, the sentence is technically grammatically OK if you allow for を好き to be correct as a recent innovation, but then it means "study likes Japanese", which was not your intention.)

I think in that case it would be 日本語の勉強が好きだ as 勉強 without する is a noun and not a verb.

furrykef wrote:
I dunno if the nuance is exactly the same or not, but in this case it seems to be unnecessary to use する to turn the noun into an verb, then の to turn it back into a noun. Or am I mistaken?

Though as nuance goes, I think the difference is something along the lines of I like to study Japanese instead of I like the study of Japanese

(EDIT: I forgot to answer to the rest of the post ... sorry)

Absolutely correct. If you want to use 勉強 as noun then it must be の and not を.

edit: Yudan answered in much more detail, but since I've already typed this I'll post it anyway.